1. Field of the Invention
The present invention relates generally to an airship and more specifically to a system for actively controlling the lift of an airship. Lift is accomplished by a first gas such as air which is located in the airship at an internal pressure which is greater than the atmospheric pressure of the air on the outside of the airship and a bag filled with helium which is located within the airship and is surrounded by the first gas. The bag located within the airship and surrounded by the first gas has enough helium in it at ambient temperature to lift all but the cargo and fuel in the airship. When the first gas and helium are both heated by a heating means in the airship, increased buoyancy due to the increase of expansion of both heated gases will lift the airship with its fuel and cargo.
2. Description of Related Art
Airships are known in the prior art. More specifically, by way of example, U.S. PreGrant Publication No. 2007/0102571 to Colting discloses an airship for lifting heavy and/or oversized loads. The airship uses the leverage of positive buoyancy to lift and transport payloads.
U.S. PreGrant Publication No. 2005/0211845 to Perry; et al. discloses a non-rigid or semi-rigid airship with a hull having a plurality of lobes formed therein. The lobes decrease the radius of curvature of the hull, thereby reducing the stress on the hull due to the pressurized lifting gas contained therein. The reduced stress allows the hull to be constructed from a lighter weight material, thus reducing the mass of the hull, and enabling the airship to carry more cargo. Flexible membranes are used to partially delineate lobes. The membranes are attached to the inner surface of the hull and a group of load lines connected to and running between the membranes form a polygon-shaped cross-sectional area.
U.S. Pat. No. 7,866,601 to Balaskovic discloses an airship shaped as an oblate spheroid and a support structure which forms a partial support for the hull. A horizontal stabilizing member is coupled to a lower surface of the airship, and a vertical stabilizing member having a first end is pivotally coupled to the airship. The vertical stabilizing member and the horizontal stabilizing member may be operably coupled to one another.
U.S. Pat. No. 7,156,342 to Heaven, Jr., et al. discloses a system for actively controlling the aerostatic lift of an airship by manipulating the ratio of air to lifting gas contained within the airship, and thus the overall mass of the airship. This manipulation is accomplished by actively compressing and/or decompressing the lifting gas or internal air, with the resulting pressure differential borne primarily by the hull and/or an internal pressure tank.
U.S. Pat. No. 6,837,458 to Swearingen, et al. discloses an airship having a hull which includes a first section having a width which varies along the selected direction of travel where the width increases from the bow of the hull to a maximum width and then decreases from the maximum width to the tail section of the first section; and a second section coupled to the first section and having a width which varies along the selected direction of travel where the width increases from a leading edge of the second section to a maximum width and decreases from the maximum width to the stern of the hull.
U.S. Pat. No. 6,793,180 to Nachbar, et al. discloses an airship hull having a plurality of flexible members disposed lengthwise about the perimeter of the airship skin. The flexible members can be held in place in sleeves on the skin of the airship where there ends are drawn toward one another by tensioning means which cause the members to bow outwardly from a central axis to provide a rigid structure for the skin.
U.S. Pat. No. 6,293,493 to Eichstedt, et al. discloses a non-ridged semi-buoyant vehicle with a pressure stabilized gasbag which has an aerodynamic shape. The gasbag includes vertical catenary curtains, a pair of first and second Y shaped catenary curtains which are coupled to the vertical catenary curtains and extend along a second portion of the gasbag and the arms of each of the Y shaped curtains are attached to the top surface and the legs are attached to the bottom surface of the gasbag.
U.S. Pat. No. 5,890,676 to Coleman, et al. discloses a neutral buoyancy fuel bladder which uses hydrogen and oxygen to power an airship. The neutral buoyancy fuel bladder includes a fuel cell, electrolyzer, and means for storing hydrogen, oxygen and water. The fuel cell uses the hydrogen and oxygen to create heat, water and current flow. An energy source transmits a beam to an energy receiving unit on the airship, and the energy from said beam is used to power said airship, and replenish the supply of hydrogen and oxygen.
U.S. Pat. No. 4,591,112 to Piasecki, et al. discloses an airship with provisions for vectored thrust provided by a plurality of controllable pitch rotor thrust producing units attached to the hull. The control systems are interconnected to be operable by a master control which establishes both similar and differential pitch settings of the rotors of selected thrust units in a manner to establish vectored thrust in directions which establish the required amounts of vertical lift, propulsion thrust, trim and control forces to control all flight aspects of the airship.
U.S. Pat. No. 4,326,681 to Eshoo discloses a lighter-than-air disc-shaped non-rigid airship having a flexible envelope within which an annular pressurized tube is positioned to maintain the flexible envelope in a saucer shape when inflated. A gondola is suspended beneath the central chamber. To maintain level horizontal flight stability, differential forces are developed by providing the central chamber with heated air and the outer chambers with a lighter-than-air gas such as helium to provide greater lift than the central chamber. Propulsion units are arranged at opposite side edges of the envelope and maneuvering is accomplished by rotating the airship.
Air vehicles that use gas that is lighter than air as a form of buoyancy control have been successfully flown for over 200 years. Common gasses utilized are helium, hot air and hydrogen. In recent years there have been many attempts to design a practical cargo carrying air vehicle that uses buoyant gas to aid in lifting the vehicle and cargo. There has been little or no success in these attempts.
The main feature required for a successful cargo carrying air vehicle that uses buoyant gas is that it needs to have the ability to vary its buoyancy in order to pick up and drop off cargo and to reduce its buoyancy as fuel is burned off.
Most applications for buoyant cargo carrying air vehicles require that the cargo be dropped off at its destination and that the vehicle then return home without any cargo. This requires that the air vehicle have the ability to vary its buoyancy by at least the amount of the cargo weight.
It has proven impractical in most cases to replace the cargo with disposable ballast like water for the return trip. Large quantities of water are not always available at the destination.
There is a solution for the fuel burn-off buoyancy problem but it involves using complicated exhaust condensation devices or nonstandard fuels such as blau gas.
Recent attempts to solve this buoyancy problem have included using helicopter like rotor lift to carry the payload and fuel, using aerodynamic lift that is generated by forward motion and helium recompression.
Rotor lift buoyancy control consumes fuel at a very high rate and is not practical for long distance use.
Using aerodynamic lift from forward motion negates one of the main advantages of buoyant gas vehicles which is the ability to take off and land vertically. Also, the aspect ratio of any wing type surface will be so low that this will again require tremendous amounts of fuel to achieve the necessary lift.
Helium recompression equipment is very heavy and the process is too slow to be practical.
Pressurized and powered hot air vehicles, like hot air balloons, have recently been developed. Size and significant fuel burn has limited their success. Very large envelopes are required as hot air lifts only about 20 to 25% of what the same volume of helium lifts. Also, these large envelopes radiate a lot of heat so that fuel burn is great.
My air vehicle design overcomes the buoyancy problem completely and efficiently.
The other problem area for buoyant air vehicles is dealing with size. Any air vehicle that uses a buoyant gas to aid in lifting payload must, by their very nature, be very large. Large vehicles are difficult to deal with when a wind storm arrives.
If hot air is the buoyancy source, you can release the hot air, fold up the envelope and seek shelter from the storm. This is not practical for a large commercial cargo carrying vehicle.
If helium or hydrogen is the lifting gas, it is too expensive and impractical to either re-pressurize the gas into high pressure containers or to vent the gas off into the atmosphere. Even if the gas were removed, there would still be a lot of envelope lying on the ground that must be secured.
The only solutions found to date to secure an airship during inclement weather are to store it in a hangar or to secure the nose of the airship to a mooring mast in an area large enough to let the airship weathervane in all directions
Large airship hangars are very expensive and prove impractical for that reason. A mooring mast is also expensive and they must be large, permanent structures for large airships.
Mooring masts do not provide the required level of protection for an airship. Many airships have been destroyed while on mooring masts in less than extreme weather. Mooring mast damage can come from many sources. Gondola damage occurs when vertical wind gusts raise and lower the airship. There have been cases where airships were raised vertically above the mast before they were forcibly returned to the ground. Airship envelopes have been torn apart by the stresses on their single point nose attachment to the mooring mast.
My air vehicle design overcomes the mooring problem and can be moored from a single point on the ground in winds exceeding 100 mph.
Another problem area for non-rigid airships is the need to make the nose of the airship less prone to implosion as a result of dynamic air pressure when moving at high airspeeds. The problem is generally addressed with nose battens which are heavy and difficult to deal with.
My air vehicle design addresses this problem in a way that will allow my design to fly faster than normal non-rigid airships.